not all memory used

[gnomek]

I have 4 GB RAM in total installed:

one module KVR800D2N5/2G
two modules KVR800D2N5K2/2G (1 GB in each module)

I use 64 bit system

uname -a
Linux 945P-DS3 3.13.0-52-generic #86-Ubuntu SMP Mon May 4 04:32:59 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux

but Kubuntu sees only 2757 MB. Unfortunately BIOS sees only 2815 MB, so maybe it is a hardware issue.

I don't have swap partition.

Motherboard model: GA-945P-DS3 (rev. 3.3)
manual
http://www.gigabyte.com/products/pro...id=2474#manual

There is a note:

(Note 1) Due to standard PC architecture, a certain amount of memory is reserved for system usage and therefore the actual memory size is less than the stated amount. For example, 4 GB of memory size will instead be shown as 3.xx GB memory during system startup.

1. I don't know if system really uses it but doesn't show it or doesn't use it at all. Can I make it to use all 4 GB?

Some output from terminal:

free -m
             total       used       free     shared    buffers     cached
Mem:          2757       1410       1347         18         68        640
-/+ buffers/cache:        701       2056
Swap:            0          0          0


sudo lshw -c memory -short
H/W path        Device     Class       Description
==================================================
/0/0                       memory      128KiB BIOS
/0/4/a                     memory      64KiB L1 cache
/0/4/b                     memory      3MiB L2 cache
/0/1b                      memory      4GiB System Memory
/0/1b/0                    memory      1GiB DIMM 667 MHz (1.5 ns)
/0/1b/1                    memory      DIMM [empty]
/0/1b/2                    memory      1GiB DIMM 667 MHz (1.5 ns)
/0/1b/3                    memory      2GiB DIMM 667 MHz (1.5 ns)


sudo dmidecode -t memory
# dmidecode 2.12
SMBIOS 2.4 present.

Handle 0x0005, DMI type 5, 24 bytes
Memory Controller Information
        Error Detecting Method: 8-bit Parity
        Error Correcting Capabilities:
                None
        Supported Interleave: One-way Interleave
        Current Interleave: One-way Interleave
        Maximum Memory Module Size: 1024 MB
        Maximum Total Memory Size: 4096 MB
        Supported Speeds:
                Other
        Supported Memory Types:
                Other
        Memory Module Voltage: 5.0 V
        Associated Memory Slots: 4
                0x0006
                0x0007
                0x0008
                0x0009
        Enabled Error Correcting Capabilities:
                None

Handle 0x0006, DMI type 6, 12 bytes
Memory Module Information
        Socket Designation: A0
        Bank Connections: 1
        Current Speed: Unknown
        Type: DIMM SDRAM
        Installed Size: 1024 MB (Single-bank Connection)
        Enabled Size: 1024 MB (Single-bank Connection)
        Error Status: OK

Handle 0x0007, DMI type 6, 12 bytes
Memory Module Information
        Socket Designation: A1
        Bank Connections: 2
        Current Speed: Unknown
        Type: Unknown
        Installed Size: Not Installed
        Enabled Size: Not Installed
        Error Status: OK

Handle 0x0008, DMI type 6, 12 bytes
Memory Module Information
        Socket Designation: A2
        Bank Connections: 3
        Current Speed: Unknown
        Type: DIMM SDRAM
        Installed Size: 1024 MB (Single-bank Connection)
        Enabled Size: 1024 MB (Single-bank Connection)
        Error Status: OK

Handle 0x0009, DMI type 6, 12 bytes
Memory Module Information
        Socket Designation: A3
        Bank Connections: 4
        Current Speed: Unknown
        Type: DIMM SDRAM
        Installed Size: 2048 MB (Single-bank Connection)
        Enabled Size: 2048 MB (Single-bank Connection)
        Error Status: OK

Handle 0x001B, DMI type 16, 15 bytes
Physical Memory Array
        Location: System Board Or Motherboard
        Use: System Memory
        Error Correction Type: None
        Maximum Capacity: 4 GB
        Error Information Handle: Not Provided
        Number Of Devices: 4

Handle 0x001C, DMI type 17, 27 bytes
Memory Device
        Array Handle: 0x001B
        Error Information Handle: Not Provided
        Total Width: 64 bits
        Data Width: 64 bits
        Size: 1024 MB
        Form Factor: DIMM
        Set: None
        Locator: A0
        Bank Locator: Bank0/1
        Type: Unknown
        Type Detail: None
        Speed: 667 MHz
        Manufacturer: None
        Serial Number: None
        Asset Tag: None
        Part Number: None

Handle 0x001D, DMI type 17, 27 bytes
Memory Device
        Array Handle: 0x001B
        Error Information Handle: Not Provided
        Total Width: Unknown
        Data Width: Unknown
        Size: No Module Installed
        Form Factor: DIMM
        Set: None
        Locator: A1
        Bank Locator: Bank2/3
        Type: Unknown
        Type Detail: None
        Speed: Unknown
        Manufacturer: None
        Serial Number: None
        Asset Tag: None
        Part Number: None

Handle 0x001E, DMI type 17, 27 bytes
Memory Device
        Array Handle: 0x001B
        Error Information Handle: Not Provided
        Total Width: 64 bits
        Data Width: 64 bits
        Size: 1024 MB
        Form Factor: DIMM
        Set: None
        Locator: A2
        Bank Locator: Bank4/5
        Type: Unknown
        Type Detail: None
        Speed: 667 MHz
        Manufacturer: None
        Serial Number: None
        Asset Tag: None
        Part Number: None

Handle 0x001F, DMI type 17, 27 bytes
Memory Device
        Array Handle: 0x001B
        Error Information Handle: Not Provided
        Total Width: 64 bits
        Data Width: 64 bits
        Size: 2048 MB
        Form Factor: DIMM
        Set: None
        Locator: A3
        Bank Locator: Bank6/7
        Type: Unknown
        Type Detail: None
        Speed: 667 MHz
        Manufacturer: None
        Serial Number: None
        Asset Tag: None
        Part Number: None

2. How can I check if it works in dual channel mode?
This Bios doesn't show it.

On page 15 of manual there is info:

2. To enable Dual Channel mode with two or four memory modules (it is recommended to
use memory modules of identical brand, size, chips, and speed), you must install them
into DIMM sockets of the same color.

So I did that, but I want to be sure.

3. Would exchanging module KVR800D2N5/2G on two KVR800D2N5K2/2G to have 4 the same modules make a difference? How can I make the most out of this motherboard memory capability?

[oshunluvr]

Could be BIOS reserved RAM for video use. Check it in the BIOS. Also, according to the web, that 945 chipset has/had memory addressing problems. Combine that with different size RAM sticks and who knows what will happen.

Another test: Remove the single 2GB stick, check RAM size. Remove the 2x1GB sticks and put in the 2GB stick and check RAM size. Compare.

Could be as simple as one of the 1GB sticks is no good or not being addressed by the BIOS at all.

[elijathegold]

Could be a bad ram chip. There should be a mem test option on the boot menu. Let it run for a few hours.

[jlittle]

No-one has mentioned reseating, or the rubber (British English; american would be "eraser") trick. Some memory problems can be solved simply by reseating (taking out and putting back in) the RAM. Take measures to avoid static electricity.

Another hack is to clean the RAM contacts with a rubber, taking care not to leave lumps of rubber on the contacts.

Could be BIOS reserved RAM for video use.

Surely not that much, over a GB.

Kubuntu sees only 2757 MB. Unfortunately BIOS sees only 2815 MB,

That's the order of difference I would expect.

Before you do too much, consider costs and likely usage. Kubuntu will run really well with 2757 MB RAM, and the improvement to nearly 4 GB will not be noticeable, unless you run some task like video editing that can use lots of RAM.

[bweinel]

From the Intel 945 Express Chipset specification (http://www.intel.com/Assets/PDF/datasheet/307502.pdf):

System Memory -4 GB maximum memory

-One or two 64-bit wide DDR2 SDRAM data channels
-DDR2 400, DDR2 533
-DDR2 667 (82945G/ GC/P only)
-Bandwidth up to 10.7 GB/s (DDR2 667) in dual-channel Interleaved mode.
-Non-ECC memory only
-256-Mb, 512-Mb and 1-Gb DDR2 technologies
-Only x8, x16, DDR2 devices with four banks and also supports eight bank, 1-Gbit DDR2 devices.
-Opportunistic refresh
-Up to 32 simultaneously open pages in dual-channel mode
-SPD (Serial Presence Detect) scheme for DIMM detection support
-Suspend-to-RAM support using CKE
-Supports configurations defined in the JEDEC DDR2 DIMM specification only

I believe your issue may be related to an unsupported memory configuration. Intel doesn't recommend, at least in their documentation, using 2gb SIMMs with this particular chipset (even though Gigabyte seems to indicate it will work.)

cheers,
bill